First layer fail with support PLA

Bambu Lab H2 Series
1

Hi,

hoping to get some help with a print fail I have not been able to resolve.
I have printed this part multiple times with the same settings and .3mf file but now after multiple tries I cannot get it to print successfully.

If i split the part and print a portion only then that pice prints flawlessly.

What makes this even more difficult to pin down is it is a 23 hour print and the fail doesn’t occur until hour 16 or so.

The issue is the first layer of standard PLA that goes down after the Support PLA layer finishes is not flowing enough so it just becomes a disaster.

However, the problem does not occur at all earlier on in the print when doing the exact same thing

Heres the fail, and below are shots of the passing parts. Ive also attached a zip with the images and the .3mf

I have tried drying filament, printing with a brand new sealed spool, changing the chamber temperature, changing the nozzle temperature etc…

The only thing I can think of at this point since this same print has printed successfully many times before is the weather

support settings:

Type Normal
Independent support layer height false
Interface pattern RectLinear interlaced
top interface spacing 0
top z distance 0.01
Z overrides x/y true
Support raft interface (PLA support material)
initial layer speed 30
Initial layer flow ratio 1.1
Independent Support Layer Height false - when on surface warping occurs

Only the final back section fails:

IMG_6392
IMG_63921920×1440 696 KB

The front keyboard section prints the first layer onto the support interface without issue:

IMG_6382
IMG_63821920×2560 1.17 MB

pass2
pass21920×1440 364 KB

pass
pass1920×1440 361 KB

rightCorner
rightCorner1920×2560 576 KB

Partial prints do not fail:

partial
partial1920×2560 1.48 MB

3mf file:

caseTop.3mf (115.0 KB)

1 Like
2

I’ve been testing more and when I cut the print and print that back end only and pause at the failing spot to inspect it is printing perfectly. Looking at all the failed full prints it’s looking like the overall flow ratio is decreasing. As if printing for 16 hours straight is causing the printers flow ratio to degrade.

3

You might be experiencing some heat creep here. After a long print the chamber temperature is increasing, and also the ambient temperature might be partially of influence here.

This heat creep can eventually cause a nozzle clog, but before that you might just have this flow issue.

You could try to open the door, or make sure you print it with a lower ambient temperature.

On top of that, make sure your filaments (especially the support material) is dry.